Electrolytic condenser



Apr 9 1935n H E, RHODES 1,997,562

ELECTROLYTI C CONDENSER Filed Oct. 18, 1934 INVENTOR ATTORNEY 5 Patented Apr. 9, 19.35

UNITED STATES.

t 1,997,562 ErncmoLrrrc coNnnNsEa Howard E. Rhodes, Floral Park, N. Y., as signor to Aerovox Corporation, Brooklyn, N. Y., a corporation of New York Application October 18, 1934, Serial No. '148,801v

l cells, more especially to electrolytic condensers.

Among the objects of the invention is to provide an electrolytic condenser of extraordinarily small bulk per unit of capacity, which shall be of low cost, in embodiments suitable for various voltage and capacity requirements substantially throughout the range in which such condensers are now used forradio, power factor correction, motor starting and the like.

Another object is to provide a condenser of the above type in which an engagement is ei.- fected between the formed foil area and the absorbent interspacer which is so intimatefas substantially to reduce or eliminate the usual small gaps which commonly give rise to a poor power factor.

In the'accompanying drawing, in which are shown one or more oi various possible embodiments of the several features ofv this invention,

Fig. 1 is a transverse sectional view on an enlarged scale, of the superposed elements from which the condenser is made,

Fig. 2 is atransverse sectional view on a greatly enlarged scale through a formed foil and the absorbent material between which it is sandwiched, and,

Fig. 3 is a transverse sectional view showing one embodiment of the completed condenser.

Referring now to the drawing,'there is shown in Fig. 1, the general more or less conventional construction of an electrolytic condenser including an anode foil I0 sandwiched between paper spacers I2 and I3, over one of which is superposed the cathode foil II. Said condenser may be at as shown or enrolled in' conventional manner as shown'in Fig. 3, as hereinafter described.

Fig. 2 discloses on a greatly, enlarged scale approidmately as viewed throug'lifa microscope, but notA to scale, the cross-sectional view of the anode ,foil with the contiguousA paper sheets 'between which it is sandwichedi. The' foil is prepared accordingto the teachingsIV of the copending application of Herbert Waterman, ,Serial No. 745,535, filed September 26th, 1934.v

vAs set forth yin that application, annealed aluminum foil prepared .with crystals of size between .001 and .00001 inch issubiected to a controlled etching process by which undercut depressions I6 are eroded intothe surface of the foil, said erosion being probably the'consequence of the removal inthe etching operation from the surfaces, of a large proportion of those crystals that have a greater amount of impurity than the body of the foil, which is preferably of purity less than .per cent and ordinarily' not less than .99.6 per cent.- 'I'he etched foil after removal therefrom of all foreign matter due to the etching operation is subjected to a film forming operation resulting in a thin cli-electric nlm I1 closely adhering to the supercial area including the various undercut depressions of the foil.

The spacers I2 and I3 according to the lpresent invention are of paper differing materially from that commonly used in wax condensers.

Paper of cotton nbre, manila rope, or alpha cellulose is desirable, provided it combines the required characteristics of high absorbency, tensile strength and a rough fibrous surface resembling a nap of felt. The paper is preferably between .001 and .005 inch thick, is devoid of sizing, uncalendered and very soft. The paper should also be pure, especially in freedom from inorganic salts, such as chlorides, sulphates or nitrates. The paper should also have tensile strength sumcient to permit winding of condensers without tearing under the tension imposed by automatic winding machines, even though the paper be wet by electrolyte. The

fibre of the paper should be relativelylong, not less than 2.5 mm, to afford a considerable nap. Such libre will become sufficiently closely intermatted to aiford the requisite tensile strength, and without resort to any considerable hydration or beating which would destroy the nap and render the surface too smooth for my purpose.

One, two, three or more sheets of the paper may be used between the two foils depending on the voltage for which the condenser is intended.

TheV condenser even though tightly rolled into ay small volume, admits of being readily impregnated by immersion in hot liquid electrolyte, which reaciily soaks up into thevery porous paper and completely permeates the latter. Of course, the electrolyte maybe incorporated in the paper beforehand, or, if desired, in the course of winding the condenser.

While marked improvements in the operation of condensers are attained by the use of the new paper interspacer with conventional foil, the use of the etched foil and the new paper interspacer in combination results in advantages considerably greater than those due to the additive advantages of the said individual elements.

Apparently, the protruding nap or -fibers I2 of the special paper used, enter the undercut depressions I6 and come into intimate contact with the film lining said depressions and thereby bring the electrolyte permeating said spacer into such effective engagement with the film that minute gaps are avoided, thereby obviating any fortuitous increase in resistance due to air gaps either originallypresent or consequent upon expansion in operation. Accordingly the power factor is kept low and the tendency to break down and to'other difiiculties is' minimized whether the electrolyte be in iiuid or in paste condition.

y:By reason of the thinness of the paper, as compared to gauze. further reduction in the physical size of the condensers is attained and, of c, there is economy of cost,'since the paper is cheaper than gauze. i

Aside from these characteristics and due to its ing operation, either before or after sealing in the final container'or both before and after sealing.

Where, as is preferable, the cathode also is preformed in the manner above set forth, the condenser will readily build up on the cathode thereof to operate on reverse polarity, should such reversal accidentally occur. It is also understood that both foils can be formed, inwhich case, the condenser is especially useful for alternating current service.

The enrolled condenser unit may be encased and provided with 'terminal facilities in any of a wide variety of possible ways.

of which clamps the cathode tab 22 against the rim of the can, which rim is rolled over at 23 to effect a closure, the cover button resting upon the inturned bead 2d of the can. The button 2i also has a positive terminal 25 about which it is molded and to the under face of which is riveted at 2 the anode terminal 26. A Vent in the form of a cork plug 28 is retained in the corresponding aperture 29 in the bottom of the can.

It will thus be seen that there is herein described apparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invention and is well suited to meet the requirements of practical use.

As many changes could be made in the above construction, and many apparently widely diierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention-what I claim as new and desire to secure by Letters Patent'of the United States is:

l. An electrolytic condenser comprising aluminum foils, intervening thin, soft, matted, napped absorbent interlay, in intimate contact therewith and impregnated with electrolyte, each of the electrodes presenting a multiplicity of minute depressions greatly to increase the effective supercial area of the foil.

2. An electrolytic condenser comprising two foil electrodes, an intervening thin, soft, nap layer of absorbent material carrying electrolyte, one of said electrodes having minute depressions, removed from its otherwise substantially fiat surface to greatly increase the effective area thereof.

3. an electrolytic condenser comprising two Lacasse electrodes of thin aluminum foil, each of said electrodes having a multiplicity of minute -depressions therein, greatly to increase the eective area of said foils, each of said foils having a film Y electrolytically pregformed. thereon to facilitate vfurther formation, and a closelymatted, soft.

thin-mapped absorbent spacer between said electrodes, impregnated with electrolyte. Y

i. An electrolytic condenser comprising two electrodes of thin aluminum foil, each of said electrodes having a multiplicity of minute depressions therein, greatly to enhance lthe effective area thereof, each of said foils having a di-electric ilxn,` the completed condenser including an inter-spacer of one or more layers of thin', soft, matted, napped absorbent material intervening therebetween and soaked with electrolyte.

5. .An electrolytic condenser comprising thin aluminum foils, each of said foils having its surface eroded at a multiplicity of minute regions distributed throughout the foil area, the entire surface being preconditioned for facility of elec.

trolytic formation, the two foils having therebetween a spacer of matted, napped, soft, longfiber paper of highlyabsorbent character, the

foils with the interleaved paper being closely enrolled, the paper interlay being impregnated with electrolyte, one of the foils having a further lm formation, constituting the product of electro' lytic action thereon by the electrolyte in the spacer.

6. An electrolytic condenser' including annealed aluminum foil having minute surface irregularities substantially exposing crystalline faces of the grain of the foil structure, and a loosely mated absorbent interspacer, presenting relatively long fibers and a nap, the latter substantially entering said various irregularities and electrolyte retained by said interspacerand the nap thereof.

grains of which are of length between .001 inch and .00001 inch and having said crystalline faces substantially exposed at the surface, with minute irregularities between crystalline y faces, from which the crystals are absent, said interspacer comprising matted cellulosic absorbent ber presenting a substantial nap entering into intimate contact with said irregularities in the foil surface, whereby to cause electrolyte incorporated in said interspacer to enter, and' remain in intimate contact with substantially the entire surface area of the foil.

, 8. An electrolytic condenser including electrode foils and an electrolyte carrying absorbent interspacer therebetween, one of said foils ofA annealed aluminum presenting a structure having crystals with faces substantially exposed at the surface and presenting minute depressions bev tween contiguous crystal faces, from which certain crystals of conventional foil are absent, said interspacer comprising matted cellulosic absorbent ber in excess of 2.5 in length, presenting a substantial nap entering into intimate contact 

